Model airplane propeller drive



15, 1955 s. D. WILLIAMSON 2,715,445

MODEL AIRPLANE PROPELLER DRIVE Filed July 12, 1954 A 1M; aw

INVENTOR.

STEWART D.W| LLIAMSON ATTORNEYS United States Patent Ofiice 2,715,445 Patented Aug. 15, 1955 MODEL AIRPLANE PROPELLER DRIVE Stewart D. Williamson, Detroit, Mich.

Application July 12, 1954, Serial No. 442,877

Claims. (Cl. 170135.4)

This invention relates to a motor and more particularly to a model airplane motor.

One object of the invention is to provide a model airplane motor having a propeller, and in which the propeller is the only moving part. In accordance with this invention, a fluid is discharged tangentially at or near the propeller blade tips to cause the propeller to spin rapidly.

Another object of this invention is to provide a model airplane motor which may be driven by a variety of fuels. Carbon dioxide, for example, is suitable since it may be contained in a relatively small cartridge under compression and when released yields a large volume of g A further object of the invention is to provide a motor having a control element which is readily accessible to control the operation of the motor.

Still another object of the invention is to provide a motor which is of relatively light weight construction, composed of a few inexpensive parts and which is easy to operate and highly eflicient in the performance of its intended function.

Other objects of the invention will become apparent as the following description proceeds, especially when taken in conjunction with the accompanying drawing, wherein:

Figure l is a side elevational view, partly in section, of a motor constructed in accordance with the present invention;

Figure 2 is a detail view in front elevation of the propeller shown in Figure l; and

Figure 3 is a detail view in longitudinal section of the valve shown in Figure 1.

Referring now more particularly to the drawing, the model airplane motor comprises a cylindrical hub 10, which may be formed of aluminum, and a propeller 12 of plastic or other light weight material. The propeller 12 has a bored central portion 14 which is rotatably mounted on the front end portion of the hub, and propeller blades 16 extend radially outwardly from the bored central portion and are suitably twisted or inclined so that upon rotation of the propeller an axial thrust is obtained.

A cartridge 18 is provided having a chamber 20 therein for containing a charge of compressed fluid such as carbon dioxide. The cartridge has a reduced neck portion 22 providing a discharge orifice for the compressed fluid, and the neck 22 of the cartridge is internally threaded. The rear end of the hub 10 is externally threaded and threadedly engages in the reduced neck of the cartridge to provide a fluid seal.

The hub is formed with a threaded through passage 24 which extends entirely from the front to the rear end thereof.

The bored central portion 14 of the propeller is formed with an annular groove 26 and the propeller blades are each formed with a radially extending internal passage 27 which opens into the groove 26. Passages 27 terminate adjacent the tips of the blades in discharge ports 28 which open exteriorly of the blades and which are directed tangentially relative to the blades. Angularly arranged ports 32 in the hub establish communication between the passage 24 and the groove 26.

A control element or cap 34 at the front end of the hub has a rearward extension 35 which threadedly engages in the front end of passage 24, the extension 35 forming a seal in the hub preventing the flow of fluid through the front end of the hub.

A valve 36 is supported in the passage 24 at the rear end of the hub. Valve 36 comprises a cylindrical hollow sleeve 38 having a threaded exterior surface threadedly engaging in passage 24 to form a fluid seal and having a conical valve seat 40 at the rear end. A valve element 4-2 at the rear end of the hollow sleeve 38 is formed to have a sealing engagement with the valve seat to prevent the flow of fluid from the cartridge in the closed position of the valve element. The extension 35 of cap 34 has a conical projection 44 at its rear end for engaging the valve stem 46 which is rigid with the valve element and extends forwardly through and beyond the hollow sleeve 38.

The sleeve 38 has annular shoulders 48 at opposite ends for retaining a coil spring 5t) within the sleeve under a slight compression. The front end 52 of the spring is secured to stem 46 to normally urge the valve element 42 against its seat. It will be appreciated of course, that the pressure of the fluid compressed in the cartridge will also act to seat the valve and in most cases this pressure is adequate even without the spring, although the latter is desirably provided as added insurance.

It will be seen that the cap 34 is formed with an annular shoulder 55 which extends radially beyond the hub and cooperates with the neck of the cartridge to retain the propeller against axial shifting movement.

The parts of the motor are shown in Figure 1 in the position for operation, and it will be noted that neither the extension 35 nor the valve 36 obstructs communication between passage 24 and ports 32. The cap has been threaded into the hub sufliciently to lift the valve element 42 from its seat, thereby opening communication to the propeller blade passages 27 from the cartridge through the valve sleeve passage 24 in the hub, ports 32 and annular groove 26. The compressed fluid from the cartridge will pass through the passages in the propeller blades and be discharged from the tangentially directed ports 28 adjacent the blade tips. Since these ports are designed both to expel the fluid in a clockwise direction as viewed in Figure 2, the reaction to the expulsion of the fluid will cause the propeller to spin in a counterclockwise direction.

It will be appreciated that in the ofl position of the motor, the cap will be rotated to cause the same to shift forwardly of the hub and out of contact with valve stem 46, whereupon the valve element 42 is seated against valve seat 40 to seal ofi the compressed fluid within the cartridge. In order to start the motor, it is only necessary to rotate the cap in the opposite direction to shift the projection 44 rearwardly, thereby to depress the valve stem and open the valve element.

The cartridge may be recharged by merely removing cap 34 and replacing it with the nozzle of suitable charging apparatus. The pressure of the charging fluid will be sufficient to unseat valve element 42 against the action of spring 50.

All of the parts are preferably made of any suitable light weight material. When employed in a model airplane, for example, suitable means (not shown) will be provided to fixedly mount the cartridge thereon.

What I claim as my invention is:

1. A model airplane motor comprising a hub, a propeller having a bored central portion rotatably mounted on said hub and having propeller blades projecting radially outwardly from said bored central portion, a cartridge having a chamber for containing a charge of fluid under pressure, a first passage in said hub communicating with the chamber in said cartridge, an annular groove in said bored central portion, additional passages in said blades opening into said annular groove, said additional'passages terminating adjacent the tips of the blades in discharge ports directed tangentially relative to said blades, angularly arranged ports in said hub establishing communication between said first passage and said annular groove, a valve in said first passage, said valve including a valve element resiliently urged to closed position normally to prevent the flow of fluid through said first passage, and means on said hub for shifting said valve element to open position.

2. A motoras defined in claim 1 having means detachably connecting said hub and said cartridge together.

3. A model airplane motor comprising a hub, a propeller having a bored central portion rotatably mounted on said hub and having propeller blades extending radial- 1y outwardly from said bored central portion, a cartridge having a chamber for containing a charge of fluid under pressure, said cartridge having a discharge orifice and said hub having'its rear end detachably connected to said discharge orifice, said hub having a through passage extending from front to rear and communicating with the chamber in said cartridge, an annular groove in said bored central portion, additional passages in said blades opening into said annular groove, said additional passages terminating adjacent the tips of said blades in discharge ports directed tangentially relative to said blades, angularly arranged ports in said hub establishing communication between said first passage and said groove, a valve in said first passage between said angularly arranged ports and the rear end of said hub, said valve including a valve element and spring means urging said valve element to closed position preventing flow of fluid from said chamber to said angularly arranged ports, and a cap having an extension threadedly received in the front end of said first passage, preventing flow of fluid through the front end of said first passage, said cap extension having a part engageable with said valve element for moving the latter to open position upon axial movement of said cap relative to said hub.

4. A motor comprising a hub, a propeller rotatably mounted von said hub and having propeller blades projecting radially outwardly from said hub, a first passage in said hub adapted for communication with asource of fluid under pressure, additional passages in said blades terminating adjacent the tips of said blades in discharge ports directed tangentially relative to said blades, means establishing communication between said first passage and said additional passages, a valve in said first passage having a normally closed valve element to prevent the flow of fluid through said first passage to said additional passages, and means on said hub for shifting said valve element to open position.

5. A motor comprising a hub, a propeller rotatably mounted on said hub and having propeller blades projecting radially outwardly from said hub, a first passage in said hub adapted for communication with a source of fluid under pressure, additional passages in said blades terminating adjacent the tips of said blades in discharge ports directed tangentially relative to said blades, means establishing communication between said first passage and said additional passages, a valve in said first passage, and means including a member on said hub for moving said valve to open and closed positions.

References Cited in the file of this patent UNITED STATES PATENTS 1,099,083 Duc June 2, 1914 2,330,056 Howard Sept. 21, 1943 FOREIGN PATENTS 20,730 Great Britain of 1908 

